<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      #box {
        padding: 20px;
        background: palegoldenrod;
      }
    </style>
  </head>
  <body>
    <div id="box"></div>
    <button id="btn1">执行计算任务</button>
    <button id="btn2">更改背景颜色</button>
    <script>
      var box = document.getElementById("box")
      var btn1 = document.getElementById("btn1")
      var btn2 = document.getElementById("btn2")
      var number = 99999
      var value = 0

      function calc(deadline) {
        while (number > 0 && deadline.timeRemaining() > 1) {
          value = Math.random() < 0.5 ? Math.random() : Math.random()
          console.log(value)
          number--
        }
        requestIdleCallback(calc)
      }

      btn1.onclick = function () {
        requestIdleCallback(calc)
      }

      btn2.onclick = function () {
        box.style.background = "green"
      }
    </script>
  </body>
</html>
